1. Field of the Invention
The present invention relates to a semiconductor module comprising a switching semiconductor device.
2. Description of the Background Art
In business of automobiles in which an environmental problem has become more serious, nowadays, a hybrid car using an engine and a motor as a driving source together has been developed to enhance a mileage and an exhaust gas characteristic. Moreover, a change of a transmission into a nonstep variable speed gear has been improved to set an operating point of the engine into a place having a better mileage or a smaller exhaust gas.
In such a hybrid car or a vehicle having the nonstep variable speed gear, each operating point of a subsystem to be equipped, for example, an engine system or a transmission system is controlled to implement driving force required for the vehicle, and particularly, to be set into the best place in which energy consumption and an exhaust gas can be reduced.
Above all, in the hybrid car, a semiconductor module comprising a switching semiconductor device provided with a switching semiconductor element for a power such as an IGBT or an MOS transistor (which will be hereinafter referred to as a “switching element”) is used for driving a motor at a desirable operating point.
On the other hand, for example, Japanese Patent Application Laid-Open No. 2000-032608 has disclosed a method of expecting a future operation of a car as well as an instantaneous energy efficiency and operating an engine at an operating point having a high energy efficiency in system total in order to cope with a strict mileage regulation in the future. In a method of discriminating the operating point, an engine operating point is changed and the best operating point is stored after trial and error. For this reason, a load related to a whole hybrid system such as a temperature at that time, an electric load state or the like is to be made clear in order to compensate for a selection of the best operating point even if other conditions are assumed to be identical.
If an external environment is varied, for example, an electric load is increased or decreased by driving a subsystem such as an air conditioner, an electric power steering (EPS) or a sliding roof or a power loss characteristic of each subsystem is changed, the best operating point is changed in a similar vehicle operation state. In that case, it is more desirable that an energy efficiency of each subsystem constituting a system should be stored corresponding to an environment which is changed momently and an energy efficiency of the whole system should be decided based thereon than the storage of the energy efficiency in only system total as in the method disclosed in the Japanese Patent Application Laid-Open No. 2000-032608. In other words, it is desirable to employ a method of storing the power loss of each subsystem constituting the system corresponding to the environment which is changed momently and deciding the power loss of the whole system based thereon.
On the other hand, as described above, the semiconductor module comprising the switching semiconductor device is used for controlling a motor of a motor system or a subsystem such as a sliding roof in a hybrid car. In order to obtain a power loss of a subsystem comprising the semiconductor module by employing the method described above, it is necessary to cause an external system of the semiconductor module to recognize a value of a power loss of the switching semiconductor device used therein.